Note: Descriptions are shown in the official language in which they were submitted.
2~-
- Sch 62 ~
Method and Installation for concentrating Heavy Metais,
Precious Metals or Heavy Minerals in sand or gravel
This invention concerns a me-thod for concentrating of
precious metals, particularly gold, heavy metals, parti-
cularly copp~r, tin, plumb, or heavy minerals, particu-
larly diamon~s dispersedly occuring in sandlgravel deposits,
and also concerns a dressing and concentrating installation~
for carrying out this method. For recovery of small gold~
grains-from al~uvial placer occurences hitherto mainly ~
so-called sluice boxes have been used, which are operating
such that grains of different specific weight are seperated
from each other along a stream of water. As the grains of
greater specific weight will be carried on by the stream
of water more slowly *han the grains of lighter speciflc
weight, they will be retarded by and will settle in front
of riffles or similar transverse obstacl~s on the bottom
of the sluice.
As alluvial deposits include materials of most different ~ -
grain si2es, and as even by screehing homogeneous fraction
of qrains cannot be a~ained economically, those sluice
boxes necessarily will be fed with bulk material of qreatlv ~ j
differninq grain sizes. Thiq is the ~ack_ground for opera- ~
_ / _
~2~
Sch 62 ~ 2 ~
ting such sluice boxes with relatively hlgh flowing velocltY,
high enough in order to be able to discharqe the earth
roof including the greatest qxain fractions and in order
to avoid obstr~ctions. However, such high flowing ~elocities
will reduce the sinkinq or qravitating velocity, and for
certain ranges of fine grain -sizes no gravitat1ng will
occur any more under those conditions.
Experience has shown that freely occuring gold (or other
heavy metals or heavy minerals) can be recovered by means
of sluice boxes only in limit~ed amounts and further only
to a certain minimum grain size. It would be desir~
to also recover these grains or Particles of gold, which
could not~gr~sped until nowl because it is indisPensa~l
for an ecomomicallY worthwhile processing of sands or
qravels bearing gold and precious metals only in very small
quantities, to previously enriching the contents of gold
or precious meta1s. respectively.
For such enr~chment a various number of dressing ox concen-
trating devices alrèady has been used, such as iigs, cone~
concentrators, HumphreY spirals, Reichert spirals, Denver
spirals operating according to the principle of use of
centrifugal force, shaking tables, or rocking and/or osci
lating washlng troughs. It has been experienced t however,
that the concentrating and classifying processes carried
out under the use of the above mentioned dressing devices
_ / _
~2131Z;~
Sch 62 ~ 3
are incapable to economically enrich or concentrate the
free gold occuring in relative small quantities within
alluvial deposits. Especially, it has been experiencedl
that any effective concentration by means o~ those Processes
can oniy''be carried out when using material of substantial
homogeneous grain sizes,.
For operating the before mentioned hydro-mechanical settling `
and/or classlfying methods for dressing of sands or gravels
of different grain,!sizes either very high flow veloci~ies
are necessary, by whlch the gravitating or depositing
velocity of the solids to be concentrated will be remarkabI~
reduced, if not eleminated at all (by sluice boxes) ,-or a
strong upwardly directed streaming is necessary obviating
a sufficient concentration. If such upwardly directed current~
are too weak, then gravel and sand will settle together
with the free solids of heavy metal or heavy mlnera~ An
concentration of the specifically heavier grains is m~ssing:
the concentrating material will get lost or agglomerate
such that the operability of the jiqs and other concentra
ting devices is lost. The precious metal to be recovered ~
is dischargecl toqether with sand and gravel to the bulk ~,
material.
It is a main ob~ect of this invention to provide a method
and a device for concentrating of free gold Partlcles (and
other free precious metal or heavy mineral particles~ occurinq
2~
Sch 62 _ 4
in sand or gra~el, wherein also ~hose grains, which have
become lost h:Ltherto, particularY particles from the
range of flnex grain sizes will be grasped, and which ln
particular~are adapted for carrvinq out ~ large scale and
therefore économical dressing o sands or gravel from
alluvial deposits i~cludinq only relative small quantities
of freely occurinq precious metals, without unusual
qreater expenses and without devices and ~quipment
specifically liable to wear.
The before mentioned and further objects can he achieved
according to the in~ention by the following characterizing
steps of the method of the kind mentioned beore:
a) Comminution of the raw material by its delivery
to a prefera~l~ oscilating or shaking conveying
means,
b) continued decomPosing of -the raw material by .
intensive spraying water QntO the raw material
and by blowinq pressurized air through the '
solid/water-mixture on its way towards a
forescreen for separation of coarse bulk material,
c) transferring the pre-classified raw m~erial as
a suspension of water and solids into screen~
devices:~or screen classification into at least
two~ preferably six fractions,
d)separate subsequent treatment of the oversize
fraction from each screeniny device by
.
~261 2~
Sch 62 - 5 ~
adding wa~er and agitating for reestablishing
a water/solid-suspension in a volumetric
relation of about 1/1,
.e) Seperate concentration of the solid/water-sus-
pensions produced from the oversize fractions
and of the undersize grain solid/water-suspen
sion formed from the last screen b~ conversion
:into a largely and substantially uniform flowing
condition having flow velocities preferably
between about 0,25 and 0r05 meter/sec. over a
:Lenght generally not surmounting 3 meter,
~) :retarding and stopping the flowing ~ondition
of the suspension into a plurallity of volumes
separated and arranged one after each:other in
flowing direction within the lower range of the
overall:height of the fluidiced bed, prefarably
at a height at about 1/3 to 2/3 of that overall
height,~
g) ~nd treatment of the respe~tive fluidiced bed
during its~retarded flow condition in its lower
range of height by means of pressure and suction
~;hocks acting onto the mixture from below~and
prefarably with a pulsation frequency in the range
between:about t~o and three ~ertz ~cycles per :~
second).
By means of the inventional proposal it has becoma posslble
the first time to handle large quantities of the material to
Sch 62 - 6 -
be treated as well for dressina as for concentrating
~ur~oses, which is a precondition for economy of operatlon
for ~reatment of raw material having a very low peraentage
of gold (heavy metals ox heav~ minerals). Already ln the
stage of feeding provisions are made such that even heavllY
argillaceous bulk mat~rials will be commlnuted and the freely
occuring particles of metal or heav~ minerals can be~
enucleated from the agglomerations, and further the m~jor
~art of the fed in raw material, as far as decomposable ~
will be factually decomposed into fractions of grain sizes
which can be subsequently treated in a relative simPle
manner.
An important feature of the inventional method is presented
by the new way of concentration of the solid/water-mlxtures
carefully Prepared after the screening oPeration , on pre-
ferably broadly and relative slowly flowing fluidiced beds=
flowing volumes , the lower portion of which has been stopped
and is exPosed to pulsations, which can be controlled accor-
ding to their frequencv and amplitude in order to achieve
a maximum of concentration. These pulsatlons are effective
to whirl up waste particles, which possibly have already
settled within the f~rst stopped volumes of the fluidiced
bed and which now will be carried away bY the flowing uPper
part of said fluidiced bed, while the mineral or metal to~be
concentrated is enabled by its greater qravity to earlier
settle, such that the concentratlon result wlll surprisingly
early raise with a number of repetitions of pulsations and
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Sch 62 - 7 -
with a number of quieted volumes one after the other in the
flow direction of the fluidi~d bed already at relatively
small lenghts between 1 meter to about 3 meter of the
fluidi~ed bed.
.- . ,
It has been found to be economical, lf the solidiwater-sus-
pensions produced after screen classification are treated~
when in the form o~ 10wing beds having a breadth preferabl~ ~ ;
between 1 and about 2 meter by means of pulsationa even
though also greater breadth of the flowinq beds would lead
to good results, while as far as the device construction is
concerned, those larger embodyments would be cumbersome to
handle. Further, preferably, the pulsations are introduced
uniformly acting over the entire length of the flowing bed
in form of a flowing flat voIume. The amplitude of the pul-
sations immediately at the driven or s~mu~ated bottom of
the flQwinq bed generallY amounts about 5 mm which however
could be increase~ , for example for fractions of greater
grain sizes! where an example of a maximum amplitude~would~
be 15 mm. At any case in practisinq of~the inve~tional method
provisions ~hould be made that the pressure and suct~on
strokes of the pulsation will have the effect that the grains
in the quieted lower Portions (settling vessels)of the flowin~
bed are whirled up or are kept in suspension such that the~
lighter waist particles are carried away by the upper flowinq
portion of the flowing bed and therefore an exchange takes
place between the wanted heavier particles and the lighter
Sch 62 - 8 -
waist and with other words an effective concentration
takes place. Dependent from the grain siæe to be treated
it may become necessary to vary the length of the ~uieted
Portions ,(settling vess~ s~ which are arranged one behind
the other'in the flowing directi.on.
If the wanted particles of gold or heavy minerals are
embedded in heavy argihaceous deposits, these argi~aceous
sands and/or gravels must be exploited and dressed~too.
Until now the placer mining industry was unable to do that,
because no correspondinq dressing method for qreater volumes
was disponible to take into account the specific require-
ments of placer mining of alluvial deposttsO As far as in
the known dressing methods for small vol~es the water
seperated are after depositing the waist material has been
freed from mud, this has been done by using drain pools or
overflow pools. Mud removal by means of drain pool necessitates
a qreat ~ettling and retaining time, which is so long that
neither in Alasca nor in Canada (Yukon) one single plant~is
instaIled which would be able to comply with the officially
issued requirements concerning the mud removal. In order to
avoid polllution or clogging of the natural waters during
application of the inventional method for handling large
volumes, according to another feature of the invention it
is proposed that the mud containing solid/water-suspension
of the fine qrain waist fraction after concéntration is
pumped onto the rubbel stone dump forminq the waist from
coarser grain size material and effective as filter , such
.
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Sch 6 2 - 9 --
that the flltered water thereafter may be recixculated.
These measures make possible and effective mud removal of
qreater volumes of water in an economical manner.
According to an inventional alternative emhodyment the
mud contalning .solid/water-mixtu~e of the fine ~rain sized
waist fraction is pumped up to a tower in order to be fed
then by gravity to hydrocyclones arranged one below the
other, wherein the method is repeated as long as at the
outlet of the last hydrocyclone clarified water is recovered
for being recycled to one of the preceding stages of the
dressing and concen~rating process. Both of the before
discribed mud removal processes can be carried out at rela-
tively low expenses, also with respect to oPerating energy.
Further, the mud removal methods can be easily integrated
into the overall process and further are efective to auto-
matically fill up again the pit exploited before.
According to another aspect of the invention a dressing
and concentrating inskalla~ion is provided for carrying
out the above described method, wherein in a raw material
feed station for conveying and comminuting especially of~
conglomerating material includes a vibratlng feed chute
having side walls, the upper edges of which are provided~
with an inwardly directéd covering edqe partly covering the
conveyor bottom, while below said covering edge no~zles
for pressurized alr and/or water are mounted and ~ch ar~
_ / _
~2~ S
Sch 62 10 - .
protected from above. Said feed ehute is followed by a
screen for removal of tumb material, while a collecting
tank is disposed thereunder for collecting the produced
solid/water-mixture.
If the alluvial deposits of sand and gravel include a greater
percentage of clay such that the vibratinq feed chute cannot
provide for an effective comminution under all conditions~
then according to the invention a conveyor belt wash street
is arrangsd in frontof said vibrating feed chute including
a plurality of relatively short conveyor belts, which are
slightly upwardly inclined in feed direction and are arranged
one behind the other such that the feed material will fall
from step to step like on stairs f~rom the end of the upper~ :
to the beginniny of the following conveyor belt. Above ~:~
said conveyor belts comminuting means.are provided, especially
in form of nozzles for pressurized air and/or water or
water showers. By means of the stair-like arranyement of ~ ~ -
the conveyor belts one arranged behind the other the bul~
material will tumble and roll from step to step. This ls
true also for the oversized material which is d~olved,
agitated and washed by means of the simultaneous use of
water and the conditioning by means of pressur~zed air streams.
For making e~fective the treatmen.~ of the bulk material
by means of the pressurized fluid jets the conveyor belt
Sch 62
washing street expediently .is mounted in a tunnel-like
housing, the bottom of which forms a conveying chute
and the clrcumferential walls thereof preferably include
jet nozzles , which are mounted such that they are dixected
from all directions to the conveyor belts extendiny along
the lonqitùdinal`centre of the tunnel. These jets will act
to fl~sh or to blow away particles of finer ~rain size of
the bulk material from the conveyor belt to the bottom
chute. The heavier and coarse bulk material remains on
the conveyor belts and further exposed to the intensive
mechanical treatment by means of the stair-like steps in
connection with the jet action.
In the raw material feed station the before mentioned
washing street in front of the vibrating feed chute can be
equipped with vibratlng conveyor channnels instead of conveyor
belts, which are arranged one behind the other in a step
like manner and are provided with perforated bottoms.
Preferably at least one vibrating conveyor channel in~ludes
a longitudinally stepped screen deck arranged above an
oscilating frame, said screen deck being arranged within
the effective range of the jet nozzles mounted on the inner
perifery of the tunnel-like housing. Similarly as the screen
deck, the conveyor belts may be also perforated or may be
carried out in form of thieves.
According to another aspect of the invention the collecting
tank arranged under the coarse screen can be e~uipped with
Sch 62 - 12 -
agitating means or with nozzles spacidly divided about the
tank walls for providing pressurized air and/or pressurized
water jets for continued disso~ving and comminuting the
solid portion of the mixture.
To the lower conically formed discharge exit oE each o~ said
collecting tanks are connected one or a plurallty of screening
machines, according to the number of the desired grain size
fractions. Each screening sta~ion is connected to a distri-
buting tank by means of a conveyor means, which, if necessary,
may be equipped with water showers. Each distributing tank
is used to simultaneously feed several or a certain number
of chamber pulsators, which are all charged with the same
solid/water-suspenslon. In the respective distributing tank
at the latest provisions are made that the suspension to be
-fed to the chamber pulsators has a relatlon of about one
part solids and about two parts~water. In a preferred embody-
ment the distributing tank has a the form o~ a vertically
disposed cyllnder with an upper conical feed hopper and a
divider cone~n the bottom and upwardly converging, while the
outflow connections are arran~ed in the bottom wall between
the cylinder and the circumference of the divider cone.
The so-called chamber p~sators, which-are fed with the
homogenized solid/water-suspension by means of channels or
pipes having flared discharge ends, according to a preferred
embodirment of the invention each comprise a trough-like
pulsator fràme with adjustable inclinination, with a bottom
2~i
Sch 62 - 13 -
in the orm of an elastic diaphragm , further comprising
transversely extending and longltudinally equally spaced
cross members or walls extending from thebottom up to a
portion o~ the overall height of the trough, said cross
walls together with the lateral walls forming a sequence
of settling.chambers or settling basins, the bottom of
which is activated for executing pulsation mQvements.
The diaphragm forming bottom of the trough can be sealedly
clamped between an upper encircling frame an a lower
pressing frame, the latter including cross members. Between
those cross members and the lowe.r edges of the cross walls
the diaphragm is supported and is pressed *ogether for ~ealing
purposes. The diaphragm may be actuated to execute pulsation
movemen~s in the area of each single settling basin by
means of a respective upwardly and downwardly moved piston,
and preferably a rocking frame commen to all piston is
driven by a suitable oscilating drive means.
In a prefe~ed embod~ment of the settling equipment according
to the invention the cross walls of the chamber pulsators
consist of U or channel profiles, the open side of which.l~ .
directed downstream, while the lower leg of this proflle~.
serves as bearing.and sealing sur~ace for the diaphragm, and
the upper leg of the profile covers about 1/3 of the length
(in flow direction) of the respective basin, in order to avoid
a too strong whirling action and an undesired scavenging
of the settling basins, especially if higher and therefore
:~z~
Sch 62 ~ 14 -
more agyressive flow velocities are used.
The invention will be further described by way of exampleswith reference to the accompanying drawings, wherein
Fig. 1 shows a more! or less schematic represen-
tation of the different steps and devices
used in the method according to the inven-
tion,
Fig. 2 a flow ~art of the inventional method
similar to Fig. 1,
Fig. 3 a schematic elevational view as longitudinal
section of a conveyor belt washing street
immedlately after the feed station of the
overall dressing and concentration ~nstalla-
tion,
Fig. 3a - 3c schema ic perspective end views of different
possible shapes of washing street tunnel or
channel;
Fig. 4 another embod~ment of a washing street imme-
diately follw~ng the feed station in similar
representation as in Fig. 3, wherein the
conveyor belts are replaced by a stepped
- vibration trough,
Fig. 4a a perspective partial end v~ew onto the
vlbration trough of Fig. 4 also showing the
perforated bottom screen of said trough,
' ,;
-15-
Fig. 4b and 4c perspective partlal end views of difEerent
possible outer shapes and su~port
arrangement of the tunnel including the
vibration trough according to Fig. 4,
Fig. 4d a schematic plan view of a vibrating or
oscillating trough similar to Fig. 4 but
consisting of a number of articulated
sections,
Fig~ 4e a schematic plan view of an alternative
construction of the vibrating trough
generally shown in Fig. 4, wherein the
cross steps are replaced by staggered
deflector means providing an extended
path and time of retaining the bulk
material to be treated on a relatively
short length of the trough,
Fig. 4f is a plan view of another vibrating trough
useful in a vibrating washing street like
Fig. 4,
Fig. 5a and 5b a schematic perspective elevation and
vertical section, respectively of a
distribution;tank to be connected between
a screening machine and an arrangement
of chamber pulsators,
Fig. 6 and 7 perspective partial views of an embodiment
of a chamber pulsator comprising an upper
trough-like frame having associated thereto
cross walls to form settling basins,
Fig. 8 another embodiment of a chamber pulsator
shown by a schematic vertical longitudinal
section similar to Fig. 7,
~,~
s
Sch 62 - 16 ~
Fiy. 9. another perspective partial representation
of the pulsating and vibrati~g frame similar
to Fig. 9 and
Fig. 1~ a supplemented perspective representation
of the pulsator sim~lar to Fig. ~ and 10.
The bulk material to be treated is brouyht. by means of a front
loader or another earth moving machine to a grizzly feeder ,
which in Fiy. ~ is schematically represented at the feeding
station 10. In this feeding chute the bulk matexial ls shower
treated at high water pressure and is agitated such that sand~
gravel is washed, argi~acous material is dissolved and an
easily flowing solid/water-mixture !i5 producedi by which
afterwards conglomeration is avoided. In order to support
the comminution action pressurized air may be introduced by
nozzles from suitable places~ The vibrating feed chute 10
indicated in Fig. ~ has side walls, the upper portions of
which are inwardly directed for covsring those water and~or
pressurized air nozzles. The dispersed and dissolved bulk :
material flows from the feeder chute 10 over a joining coarse
screen 12 in order to discharge the coarse material either
by a chute or an intermediate conveyor belt 14 to the waste
conveyor beLt street 16 . Conse~uently, the coarse screen 12
removes in this method the washed tun~ material as overgrain
from the further dressing and concentration process.
According to an alternative embod~ment the bulk material to
be treated is fe~d to a apron feeder A (Flg. 1) having strong
lateral walls similar to the lateral walls of the v~bration
~2C~2~5i
Sch 62 - 17 -
feeder trough, which side walls form an openlng at the dis-
charge end. The upper edges of the side walls have an
inwardly directed edge portion for protecting the water and/
or pressurized air nozzles for comminution of the bulk material.
As the apron féieder inc~udes transverselly extending spaces
great enough, for loosing,water and solids of smaller gra'in
size, a collecting tub is disposed under this apron conveyor
having a forward inclination and an outlet towards,the
coarse screen, wherefrom the washed tumb minerals as over
size grain are discarded from,the further dressing process.
In the embod~ment shown i.n Fig. 1 , in consideration of the
different heights at the pit the apron feeder A is followéd
by a bucket conveyor ox elevator B for transporting the~more
or less completed material suspension, which can be achieved
by a non-represented treatment with water jets into a vibra-
tion trough C having a coarse scre~n. The side walls of the
bucket conveyor are elastic such as to get expanded and
streched when the respective conveyor portion is returned
at its ends.
The vibration,trough C substantially corresponds to the vibra-
tion feedex trough or chute 10 in Fig. 2 with the difference
that the material fed by the bucket conveyor B is already
more or less treated and dissolved.-
r~ ,According to a prefered emhod~-ment shown ln Fig. 3 the vi~
bration trough C in Fig. 1 or at 10 in Fig. 2 have arranged
in front of them a conveyor belt washing street. It~consists
_ ~ ~2¢ ;~5i
-18-
of any suitable number of conveyor belts 20 in
stepped relationship to each other for conveying
the bulk material in flow direction. The length
of the conveyor belts depends on the desired length
of the washing street and the desired number of
steps in the overlapping range between two belts.
This stepped arrangement has the function that the
bulk material will roll and tumble from step to
step as to dissolve thereby, in connection with
the water and pressurized air jets the coarser
grain sizes.
The vibration trough C of Fig. 1 substantiall~
corresponds to the vibrating trough of the grizzly
feeder 10 in Fig. 2 with the difference, that the
material brought ~long with th~-bucket--elevator s is
already more or less disintegrated. As a further
variant charging of material onto the apron conveyor
A of Fig. 1 does not yet need to be treated by
showering or water and pressurized air jets such
that the material until reaching the vibrating
trough C is just exposed to the disintegrating
forces during the feed action of the transpor-t
conveyor belts B.
2~i
Sch 62 - 19 -
This step-like arrangement causes the bulk material to tumble
from step to step such that espe!cially the coarse fraction
and aggomerations ar exposed to the treatment by the water
and pressurized air jets for being washed and dis~ntegrated.
The conveyor belt washing street according to Fig. ~ is
accomodated in a tunnel-like housing 22y the bottom of which
forms a trough, wherein the disintegrated material falling
from the conveyor belts will be further treated by tumbling
flowing along downwardly. No~zles for pressuriæed water and
prelssurized air are disposed around the peripherie of the
tunnel-like housing at locations effective for disintegrating
the bulk material. Each conveyor belt of the washing street
either may be arranged in a horizontal or in a slight
ascending or slight descending orientation~ Further the
bottom trough 24 with its steps 26 and the driven for a
vibrating movement, may be separatly or together with the
entire tunnel-like housing 22. Generally, material falling
down from the conveyor belt is fed by gravity to the exit of
housing 22 just by the downward inclination of khe trough 24
i e. the entire housing 22.
During normal operation of the washing street according ~o
Fig. ~ only the coarse bulk material remains on the conveyor
belts 20 and will be discharged at the exit of the washing
street. On this conveying path the bulk material will be
exposed to a continuous mechanical treatment and also to the
water and/or air jets acking from all sides onko the bulk
_ J _
~;2Z~
Sch 62 - 20 -
material tumbling from step to step. Such a washing street
allows cleaning, tumbling and washing of greater bulk material
volumes i, especially the disintegration of argillaceous
conglomerations until being discharged into the feeder like
station'C''similar to the feeder station C in Fig. 1.
Fig. ~a, 3b and 3c just serve to illustrate that the tunnel-
like housing of the washing street may have any desired
cross section such as the octogonal cross section of Fig. 4a
or a mere circular cros~ section of FigO 4c, while it is
shown in Fig. 4b that the tunnel ~ust not be entlrely closed
at its coverside but ma~ e open to form a kind of channel,
which may be assembled, for example from a number of sections
following each other in axial direction as shown in~FigO,4c.
Instead of the conveyor belt wa~hing street according to ~
Fig. 3 a vibration feeder trough washing street according to
Fiq. 4 may be arranged in the Process forwardly from the~rlzzly
feeder C in Fig. 1. As shown in Fig. 4, the step-like a~rranged~
conveyor belts are replaced by a stepped arrangement of~roughs~
30. The bottom surfaces of the feeder troughs 30 are per
forated such that material of fine grain slze may pass through~
to the b'ottom of the tunnel-like housing 22. The stepped ;~
arrangement of feeder troughs 30 are mounted on an osci~àting~
frame 34. The bottom of the housing 22 may have a stepped
surface 26 as shown in Fig. 3, and the perlpher ~ of the
housing 22 may also be equipped with nozzles 2B for pressurized
water ~ets andior air jets.
.
_ / _
.
Sch 62 - 21 -
In the s~hematical ènd view of Fig. 4a the vibrating trough 30
is seen with its perforated bottom surface, the side walls
of the trough and the vibrating frame 34 including longitudinal
frame members to support the sides of th~ trough.
As shown in Fig. 4b one exemplary form o the housing 22~1s
resiliently supported on a stationary frame in order to be
vibrated by any suitable vibration drive source with vertical
vibration displacement. It can further be seen from Fig. 4b
that the upper slde of the housing may have a pivotally mounted
cover portion. Fig. 4c serves to indicate that the cover
portion of the tunnel-like housing may be separately mounted
and supported from the bottom portion or channel portion of
the housing 22. Preferably, the cover portion is e~uipped with
the nozzles for air and water jets.
According ~o another embodiment shown in Fig~ 4d the vibratlon
trough having any desired length may consist of a number of
sections, one behind the other and each of them individually
supported by springs or on elastic material, allowing oscila-
ting movement of each section stimulated by magnetic means,
for example or by unbalance or by ex~entric weight. Each
section of the trough or housing o the washing street shown
in Fig. 4d tapers at its exit portion, which allows osci~a-
tions independent from any oscilation movement of the adjacent
sections.
The schematic side view or longitudinal section of Fig. 4e
serves to indicate that the vibrating trough washing street
,.,; _ / _
~20Z%BS
Sch 62 - 22 -
includes at least one upper arrangement of stepped sieve or
screen sections and a lower stepped bottom below the screens.
Either the screen arrangement or the entirety of screens and
bottom, i.e. the overall housing are driven for oscilating
movement. Of coarse it may be possible to have mounted
within the housing two or more screen decks one over the other
in order to produce already at this stage of ~he dressing
process a determined number of different fine grain sizes
so to save special screening machines ~n the more downstream
portions of the process. If several screen decks are arranged
one about the other, eventually only partially overlapping
in longitudinal direction the lowest screen deck above the
bottom of the trough will carry and transport a medium grain
size, while the finest grains will flow on the bottom of the
trough.
According to the plan view of a vibrating trough of Fig. 4f
to be used in a vibrating washing street like in Fig. 4 the
major part of the material flow is in transverse direction
by means of buffles or deflector means 40 according to the
indicated direction of ~he arrows. Such arrangement may be
used with advantage for installations, where the overall
length of the washing street must not be too long. Again in
this embodiment the flow of material takes place by action
of gravity i.e. by a downwardly inclination of the trough
sections having the indicated buffles. As a general remark
it should be ~oted that the before discribe~washing street
may also be composed of rigid trough sections alternating
with oscilating trough sections or housing sections.
Sch 62 - 23 -
Further in the flow chart of FigO 1, the solid/water-mixture
including the undersized grain, which is separated from the
deads in the forescreen t for example shown at C in Fig. 1
and 3 is collected in a collector tank D below that fore-
screen. The forescreen can be used in connection with an
installation~:having nozzles to direct water and pressurized
air jets towards the material to be treated. The forescraen
can further be embodied as a stepped arrange~ent of screens
to further reduce and disintegrate the deads by the effect
of tumbling from step to step.
The collecting tank D has a downwardly converging bottom,
which is also inclined towards the discharge end fo~ self
emptying operation~ The discharge opening of the collector
tank may have a closure device which makes possible automatic
opening and closing. The entire installation may be electro-
nically controlled according to the interlock system such that
by break-down of one step of the process all other steps
beginning with the first step the functions are automatically
stopped in a programmed ~e~uence.
With reference to Fig. 2, solid/water-mixture present below
the forescreen 12 in the collecting~tank D is mixed and held
in suspended condition by using a mechanical agitating devi~e
and/or by introducing pressurized water or air jets into the
mixture by vertically and horizontally directed nozzles in~the
walls of the tank. This operation is also effective to addi-
tionally dessolve and disintegrate the material to be treated.
The before described operations take place in a first stage
..
~. ~
Sch 62 - 24 -
or station of the process and all devices belonging thereto,
similar t~ all other following stages or stations may be mounted
on skids or slide pats for easy transport reasons.
.
The waste material coming from the di-fferent stations of the
process is conveyed to the waste conveyor belt street 16 for
finally being transported to the pit, which has been excavated
before. At the end of the waste conveyor belt street 16,
according to Fig. 1 and 2 a slewable conveyor belt 38 may be
used to discharge the waste material in form of a semi-circle
about the width of the pit to be re-filled.
The second stage of the process is incorporated by an osci~ating
screening machine G for seperating the different grain sizes
from the solid/water~mixture as presented in the collecting
tank D. This classiying operation allows to feed the settling
machines or devices of third method stage with material,~wh~ch,
if not already consisting of homogeneous grain sizes, at least
including one fraction o grain sizes i.e. below a certain ~
mesh size, for example. In such case the different grain sizes
of the classified fraction even the greater siz~d particles of
sand or gravel have a~smaller settling velocity than the smallest
grains (of precious metal, heavy minerals or the like~ to be
concentrated.
As shown in Fig. 1 the suspension from collector tank D is
fed by means of bucket conveyor E and a feed hopper F to the
oscilating screening machine G. The bucket conveyor feeder may
be provided as a transportable and height adjustable unit, '
Sch 62 - 25 -
which can be incorporated into the second stage of process
without any difflculty.
According to Fi~. 2 the bucket conveyor E can be dispensed
with, if.the forescreen 12 is at a level high enough in order
to provide.a~sufficient slope or inclination towards the
screening machine G and in order to make possible the arrange-
ment of a chute or hopper to feed the material to the upper
screen deck of machine G. Under these conditions further the
collecting tank D under the forescreen C would not be necessary.
The chute 40 of Fig. 3.~may be equipped with buffle plates or
additionally with a vibrating drive for further disintegrate
argillaceous material.
The oscilating screening machine G ~horizontal or vertical
osci~ator) at least comprises two screen decks in order to
produce at least three fractions of grains. The upper deck
for example has a mesh opening of about 37 mm, while the lower
screen deck has openings or meshes not greater than 8 mm. The
oversized grain of the second screen deck then includes a :
grain fraction between 8 mm and 37 mm, while the undergrain
in~ludes grains between O and 8 mm diameter. These dif~erent
fractions are seprrately from each other introduced into
settling:machines for concentrating the precious or heavy metal
or heavy minerals included therein.
Even though the concentration technique applied in the inven-
tional method provides excellent results also for bulk material
with very different grain sizes, nevertheless it may be desirable .
to use more than only two fractions in connection with only two
Sch 62 - 26 -
screen decks. Therefore , two Ol- more screen machines may
be arrange~ ne behind the other in order to provide for a
greater number of grain fractions each including a smaller
range of grain sizes, which will lend to better quality and
greater quantities ~n the screening operation. When using two
screening machines one behind the other the first one may
comprise three screen decks, while the second will only have
two screen decks.
The grain frations~produced in the screen machines are fed by
a stationary or vibrating chute ~I (Fig. 1) to the assoc.iated
settling machine. As the overgrain in the screening machines
is produced substantially dewatered, these fractions, if
advisable, may be transpor*ed by means of conveyor belt~:to
their associated material distributers I, from which the settling
machines are directly charged. The last undergrain fraction
includes the essential portion of water whi.ch has been added:
during the screening:steps. This grain fraction at any case
will form a solid/water-miXture having a relative high percentage
of water and so may be pumped or directed to the~associated
material distributer I by a chute.
The distributors I1 and I2 shown in Fig. 1 and 2 form an
intermediate stage o~ the process, wherein the material to be
treated is kept in suspended condition, for example by means ~
of buffle plates within the distributors, which must be passed
by the mixture of solids and water. The turbulent condition
of the material can be brought about by mechanical agitation
or by means of hori~ontal and vertical nozzles mounted within
:~2~2~
- 27 -
the distributor tank for generating jets of water and pressurized
air. All distributor tanks I are additionally fed with water
with the exception of the distributor I containing the under-
grain coming from the last seperating screen of the screening
machine. In cases where the material to be concentrated is
transported from the screen to the distributor tank by means
of a chute, then the water may be already added at this time
to improve the slidability of the material.
A convenient embodiment of the material distributor I is
shown in Fig. 5a and 5b including a hopper-like upper feed
opening from which the material will hit on a lower cone
serving an even distribution and turbulence of the suspension
fed. Surrounding the base of the cone there is a number of
discharge openings in the bottom plate of the distributor
tank each opening being connected to an associated settling
mach~ne.
In a third essential stage of the process the inventional
operation of concentration is carried out in so-called chamber
pulsators, each ~ulsator machine comprising any suitable
number of settling basins arranged one behind the other, while
the bottom of each settling basin will be pulsated, i.e. is
raised and lowered in a pre-determined rhythm and frequency.
~ach settling basin of the arrangement within a pulsating
machine is closed on five sides. Those pulsator machines are
indicated in Fig. 1 and 2 at K, while Fig. 2 somewhat in the
form of a plan view reveals that dependent from the volume of
suspension to be treated for every fraction of grain sizes a
smaller number of pulsator machines K arranged side by side
..~
~"
Sch 62 - 28 -
are fed by the distributor tank I1, while a greater number
of those pulsator machines K are fed by the distributox I2.
According to the representations of Fig. 6 - 10 each chamber
pulsator 50 includes an upper pulsator frame 52 comprislng
side walls 54 extending in flow direction and belong:ing to
a channei or trough having a certain inclination downwardly
in flow direction. The bottom of the trough is formed by a
diaphragm 56, which according to Fig. 10 is laterally supported
on a pressing frame 58 and is sealedly connected alonq the
sides of the trough with the upper pulsa-ting frame 52~ The
pressing frame 58 further supports the diaphragm by means
of spaced transvers~lly extending cross~members 60.
Upwardly from those cross members there are cross balls 62
arranged between the side walls 54 dividing the trough of
the pulsating machine 50 into a sequence of settling basins
64. It may be seen especially from Fig~ 8 that the bottom
forming diaphragm 56 between consecutive cross members 60
is not supported and therefore may be actuated there to
execute pulsat~ions of the corresponding associated settling
basin 64.
The cross walls 62 accordinq to the embodiment shown in
Fig. 6 and 7 consist of rectangularly bent sheets having
their lower sides in sealed connection with the diaphraqm 56.
In. the embodiment shown in Fig. 9 the cross walls 62 consist
of U-profile members, the open side of which is directed
downstream and so partially covering the associated settling
~2~1iZ~35
Sch 62 - 29 -
basin at its upper upstream end. The side walls 54 ovextop
the cross walls 62, as the flowing volume (fluidiced bed)
in each chamber pulsator 50 extends to a height, which is
greater than the height o the calmed settling basin, this
remaininq height of the flowinq volume dekending to some
extent on the adjustable inclination of the pulsator trough.
As can be seen from Flg. 10, the unit foxm by the upper rame
52 , pressing frame 58 and the diaphragm 56 is supported on
a machine frame and is pivotally connected thereto by h:inge
means 66 such that the unit can be upwardly tilted for emptying
the settling basins 64. According to Fig. 9 a pulsator piston
68 is disposed beneath each settling basin, said pistons
having the form of cross members and being mounted to a
common oscilatinq frame 70. This osci~ating frame 70 is supported
against fallinq down to the bottom by means of butt straps 72
extending downwardly from the pressing frame 60 and by support
bolts 74 secured to said straps 72, as shown in Fig. 9 The
rhythmic raising and lowering of the osciDating frame 70
causes the strokes of the particular portions of the diaphragm
in ea~h settling basin 64.
The mechanical drive for the pulsator movements can be effected
on the osci~ating frame by means of rotatable and excentrically
operating means. Further, the osci~ating frame can also be
driven to execute vibrations or pulsations under the use of
a polygonal disc, which is fixed on a rotating shaft. For
example, the polygonal disc is in engagement with a roller
mounted on the osci~ating frame such that during every revolution
of a hexagonal disc the roller and the oscilating frame will
_ / _
2~5
Sch 62 - 30 -
experience a number of strokes or pulsations correspondiny
to the number of corners on the disc. Pulsation drives of
this kind can be provided at one or at both ends of each res
pective pulsator machine. Preferably the pulsator drives are
infinitely variable. Another kind of driving the Pulsator
machine consists in driving the osci~ating frame by means of
hydraulic or pneumatic cylinders to execute oscilating move-
ments.
~n important contribution to the concentrating effect of the
settling machine consists in that the expandible or flexible
bottom of the series of settling basins 64 arranged one
behind the other is rhythmically raised and lowered, and in
that as well the amplitude as the frequency of oscillations
can be controlled. Further it is desirable to have the incli-
nation of each single chamber pulsator adjustable.
As shown in Fig. 1 the screened fractions produced in the
screening machine G are fed by a chute H1 or bucket conveyor
H2 to the distributor tanks I1 and I2, respectively. The waste
material produced in the chamber pulsators K may be further
treated on a dewatering screen L~ The sePerated overgrain is
directly discharged to the waste conveyor belt 16, while
the undergrain is transported directly to ~he dump, where the
watercontents are automatically filtered, or the sludge is
pumped to a conveying tower 80 supporting a number of hydro-
cyclons 82 one above the other. The heavily concentrated
sludge from the lower discharge end of the cyclones is trans-
ported to the dump, while the recovered water is recirculated
into the dressing and concentrating process.
Sch 62 - 31 -
Tests with prototype of the inventional chamber pulsator have
been carried out with the cross walls 62 having a height of
45 mm and a width (length) of 210 mm. The oscillating frame
with its upwardly protruding laterally extending pistons 68
was driven by means of hexagonal discs causing a stroke of
6 mm upwardly and downwardly.
It is the obiective oi the inventional pulsaking machine to
provide a constant rhythmic thrust and suction effect and
thereby a steady and smooth rollinq around of the material to
be concentrated, which should be carried out completely in-
dependent from the nature of the material to be treated.
Tests have shown that the inventional machine operates as well
as effective in the treatment of argillaceous sand or gravels
as in the treatment of material free of clay~ The continuou~
rhythmic thrust and suction movement of the pulsating machine
effected by raising and lowering the diaphragm, are operable
to produce a concentration of the goods to be treated and
also avoid conglomeration of the material within the settling
basins.~Another invenkional result is the mechanical charge
of specifially lighter bodies , i.e. the discharge of sand
and gravel particles , which is also enhanced by the stream
of water and its flow velocity dependent from the inclination
of the pulsator trough. During the tests the inventional
machine has brought about concentrations in some of the
settling basins, such that a concentrated gold content of
more than 90 % became found.
- ~2~1Z~
Sch 62 - 32 -
If for example gold bearing sands or gravels are treated
duxing a certai.n period For being concentrated by the inven-
tional pulsator machine, then time by time all settling
basins will have been filled with gold. It is recommended
the material to be treated only to feed during a certain
period to the pulsating machine and to treat it therein as
long as necessary to get a gold deposit in the first two
thirds of all settling basins are at least partially filled
with the material to be concentrated. For emptying the
settlinq basins the pulsating machine and consequentlY the
entire installation may be shut down.
A number of alterations and improvements may be made in the
inventional process and devices without leaving the ~cope
of invention~ The pulsating machine may get a locable cover~
which is possible, as no accumulations or conglomerations
can take place within the settling basins.
In the tests carried out with the prototype of the inventional
pulsatox machine a heavily argillaceous bulk material has
been used, wherein the grain sizes differed between a minimum
of about 0,01- mm until a maximum of about 7 mm, in order to
test the functionality and the capacity of the settling machine
under the most dificult conditions which can occur in the
concentration of precious metals (particularly gold) , heavy
metals and heavy minerals (especially diamonds) in sands or
gravels of alluvial deposits.
The waste of these tests became afterwards treated on a
shaking table and became investigated in view of eventual
2~
Sch 62 - 33 _
remaining contents of gold. As no gold could be determined
any more it can be stated.that the inventional method and
devices are particularly adapted for concentration of precious
metal particles or heavy minerals in sands and/or gravel of
alluvial deposits to an extent , which could not be achieved
at all with the method and devices according to the prior art.
The capacity o~ the inventional installations may range for
example between 50 m3/h up to 3000 m3/h.
